Adaptive composition dynamically and opportunistically uses and combines resources to best satisfy user requirements. However, when available resources cannot satisfy those requirements, no guidance or alternative options are offered by existing composition solutions. In this paper we address this issue by presenting an approach that tries to find substitutions for unavailable resources while satisfying the initial requirements. If no satisfactory substitutions are found, we relax some requirements to generate alternative compositions. Given that this relaxation (requirements adaptation) might be unbounded, we need to limit the search space while offering alternatives on the edge of the bounded solution domain. Requirements adaptation is guided by the resources available. Our approach ensures that alternative compositions are given to users based on the resources available. We demonstrate the validity of our approach by implementing a prototype tool and applying it to support individuals in meal planning to reduce food waste.